Port rally plugins to use proper modules

Sometime ago, all OpenStack related stuff moved from the main repository
to the separate one - https://github.com/openstack/rally-openstack .
All further development and maintance will be done only in a new
repository. As for first major release, the structure is not changed, so
only imports should be changed.

Depends-On: I3446ccd5a36cb686282e85a9ea210d1723da1fef
Change-Id: Ied6b0693ba2e050b0d5f5bae91fed25891ae9882

rally-scenarios/plugins/context_plugin_ec2_creds.py

@@ -16,10 +16,10 @@
 from rally.common.i18n import _
 from rally.common import logging
 from rally.common import utils as rutils
-from rally import consts
-from rally import osclients
-from rally.plugins.openstack.wrappers import network as network_wrapper
 from rally.task import context
+from rally_openstack import consts
+from rally_openstack import osclients
+from rally_openstack.wrappers import network as network_wrapper
 
 
 LOG = logging.getLogger(__name__)

rally-scenarios/plugins/context_plugin_images.py

@@ -15,9 +15,9 @@
 from rally.common.i18n import _
 from rally.common import logging
 from rally.common import utils as rutils
-from rally import consts
-from rally import osclients
 from rally.task import context
+from rally_openstack import consts
+from rally_openstack import osclients
 
 from ec2api.tests import botocoreclient
 

rally-scenarios/plugins/ec2api_plugin.py

@@ -11,9 +11,9 @@
 #    under the License.
 
 from rally.common import logging
-from rally import osclients
-from rally.plugins.openstack import scenario
 from rally.task import atomic
+from rally_openstack import osclients
+from rally_openstack import scenario
 
 from ec2api.tests import botocoreclient